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NOVA scienceNOW: Pandemic Flu

Viewing Ideas

Before Watching

1. For background information on viruses and the diseases they cause, including influenza, see the classroom activity, "Modeling an Avian-Human Hybrid Flu Virus". Review the difference between viruses and bacteria, and provide examples of illnesses that each can cause.

2. The avian influenza virus (called H5N1) that is currently circulating has caused outbreaks in poultry populations since mid-2003 in the following countries: the Republic of Korea, Vietnam, Japan, Thailand, Cambodia, Lao People's Democratic Republic, Indonesia, China, Malaysia, Russia, Kazakhstan, Mongolia, Turkey, and Romania. Some of these countries, such as Japan, Malaysia, and the Republic of Korea, believe they have controlled the disease. Human H5N1 cases have occurred in Cambodia, Indonesia, Thailand, Vietnam, and Hong Kong. Write these countries on the board. Provide atlases and blank world maps (showing country divisions) to pairs of students and have them locate and label these countries.

3. Human influenza A spreads when an uninfected person touches contaminated surfaces or inhales viruses emitted by an infected person through coughs or sneezes. To help students understand how quickly an influenza infection can spread, have them perform the following activity. Make teams of four students. Provide each team with a package of colored dots, stickers, or labels. Each team should have a different color. In round 1, tell teams to stick a label on the hands of two students (i.e., one hand of each student) from another team and also give these students a sheet of their labels. Now, many students will have a label on their hands and two sheets of labels, their own team's original color plus the one they just received. In rounds 2 and 3, repeat the process. Select a color to represent the influenza virus (e.g., red). Ask: How many in the class were originally infected with the virus? How many had the infection after three rounds? Typically, adults are infectious from the day before symptoms appear to about five days after symptoms appear. Children can be infectious for many days before showing symptoms and for as long as 10 days after symptoms begin. The 1918 influenza pandemic took only two years to spread worldwide, killing about 50 million people. Have students brainstorm places where influenza A viruses could quickly spread, such as crowded buses.

4. About 675,000 Americans and about 50 million people worldwide died in the 1918 flu pandemic. Help students develop a sense of the enormity of the pandemic by having them compare their state's population to the number of people killed by the pandemic in the United States and across the globe.

After Watching

1. Viruses are so small that scientists must use electron microscopes to see them. Have students study the number line to help them understand the size differences among viruses, cells, and larger organisms. Then ask them to fill in the table and write a size-comparison analogy for two of the number line's organisms or items. For example, viruses are about 100 times smaller than animal cells. If a paper clip (about 3 cm) were to represent a virus, then an animal cell would be the floor-to-ceiling height of an average room (about 300 cm).

2. Download the classroom activity, "Modeling an Avian-Human Hybrid Flu Virus" to teach students about the structure of influenza A viruses, how they replicate in a cell, and how, when a person is infected simultaneously with an avian and a human virus, their RNAs can mix. The hands-on activity has background information, illustrative diagrams, detailed teacher notes, discussion questions, answers, standards correlations, and student sheets. Using the worksheet, students make avian and human influenza A virus models, infect a lung cell, and make a hybrid virus that has some avian and some human RNA segments. They will see that the hybrids have surface proteins from both the avian and human influenza A viruses. Unfortunately, the human immune system does not quickly recognize this combination of surface proteins, making it particularly dangerous.

Web Sites

Key Facts About Avian Influenza, or (Bird Flu) and Avian Influenza A (H5N1) Virus
www.cdc.gov/flu/avian/gen-info/facts.htm
Includes specific information about avian Influenza in Asia and Europe.

More Flu Viruses Around than Expected, Mutate in Unexpected Ways
accessexcellence.org/WN/SU/flugenestorynov05.htm
Explains viral co-infection and reassortment, and discusses the 1918 flu.

Scientists Identify Step in Process of Flu Virus Infection
usinfo.state.gov/gi/Archive/2005/Oct/24-394830.html
Details how a flu virus infects a cell.

Tiptoeing Around Pandora's Box
www4.od.nih.gov/oba/RAC/SSSept04/pdf/Flu%20biosafety%20Science%20July04.pdf
Describes the structure of avian and human influenza and how the two virus genomes can reassort in a host cell.

WHO:H5N1 avian influenza: a chronology of key events
who.int/csr/disease/avian_influenza/chronology/en/
Dates the spread of avian influenza and explains each case.

Books

Essential Cell Biology by Bruce Alberts, Dennis Bray, Alexander Johnson, Julian Lewis, Martin Raff, Keith Roberts, and Peter Walter. Garland Publishing, Inc., 1998.
Covers cell biology topics, such as proteins, DNA, protein synthesis, genetics, and many more. High school and college textbook.

Killer Diseases by Hazel Richardson and John Gribben. Dorling Kindersley, 2002.
Introduces and explains many deadly diseases and how they spread, and includes a glossary.